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Metal-backed versus all-polyethylene unicompartmental knee arthroplasty

Scott, C. E. H., Eaton, Mark, Nutton, R. W., Wade, F. A., Evans, Samuel Lewin and Pankaj, P. 2017. Metal-backed versus all-polyethylene unicompartmental knee arthroplasty. Bone and Joint Research 6 (1) , pp. 22-30. 10.1302/2046-3758.61.BJR-2016-0142.R1

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Abstract

Objectives Up to 40% of unicompartmental knee arthroplasty (UKA) revisions are performed for unexplained pain which may be caused by elevated proximal tibial bone strain. This study investigates the effect of tibial component metal backing and polyethylene thickness on bone strain in a cemented fixed-bearing medial UKA using a finite element model (FEM) validated experimentally by digital image correlation (DIC) and acoustic emission (AE). Materials and Methods A total of ten composite tibias implanted with all-polyethylene (AP) and metal-backed (MB) tibial components were loaded to 2500 N. Cortical strain was measured using DIC and cancellous microdamage using AE. FEMs were created and validated and polyethylene thickness varied from 6 mm to 10 mm. The volume of cancellous bone exposed to < -3000 µε (pathological loading) and < -7000 µε (yield point) minimum principal (compressive) microstrain and > 3000 µε and > 7000 µε maximum principal (tensile) microstrain was computed. Results Experimental AE data and the FEM volume of cancellous bone with compressive strain < -3000 µε correlated strongly: R = 0.947, R2 = 0.847, percentage error 12.5% (p < 0.001). DIC and FEM data correlated: R = 0.838, R2 = 0.702, percentage error 4.5% (p < 0.001). FEM strain patterns included MB lateral edge concentrations; AP concentrations at keel, peg and at the region of load application. Cancellous strains were higher in AP implants at all loads: 2.2- (10 mm) to 3.2-times (6 mm) the volume of cancellous bone compressively strained < -7000 µε. Conclusion AP tibial components display greater volumes of pathologically overstrained cancellous bone than MB implants of the same geometry. Increasing AP thickness does not overcome these pathological forces and comes at the cost of greater bone resection.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Engineering
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Uncontrolled Keywords: Unicompartmental knee arthroplasty, Bone strain, Finite element analysis
Publisher: British Editorial Society of Bone and Joint Surgery
ISSN: 2046-3758
Date of First Compliant Deposit: 18 January 2017
Date of Acceptance: 20 September 2016
Last Modified: 26 Sep 2018 22:20
URI: http://orca.cf.ac.uk/id/eprint/97521

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